Cathode-ray apparatus



Jan. 14, 1947. R. E. MOE 2,414,323

CATHODE RAY APPARATUS Filed Sept. 28. 1942 1, FOCUS E con/mm 428 UNITE/q Irwventor": Robert E. Moe,

by JV ff/1W His Attorneg.

Patented Jan. 14, 1947 UNE'E'ED STATES PATENT General Electric New York Company, a corporation of Application September 28, 1942,Serial No. 459,894

'7 Claims.

1 My invention relates to cathode and it has for its object to effect certain improvegeneration of the utilized to control sweep, of the cathode ray in periodically varying voltages the deflection, or such apparatus.

fiMore particularly my invention relates to cath- OL. e

of the cathode ray device.

In such apparatus the deflection voltage is synchronized with the radiated pulses usually by voltages derived from the transmitter. ject of my invention is to provide such a system in which the synchronizing voltage is not operating, from a source of fixed frequency such as that from which operating voltage for the cathode ray device is derived.

the operating voltage.

A further object of my invention is to effect certain improvements in the deflection voltage generator whereby chronized by pulses derived from these difierent sources, even though such pulses be of diflerent polarity.

which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and through space to a remote object !2. such, for examolaas a remote aircraft. or other reflector of radiant energy, whereby they are reflected back ing discharge devices I and 2.

to a receiving antenna I3 of a pulse receiver I l associated with the transmitter.

Of course, the outgoing radio frequency pulses which are indicated at I5'in Fig. 1 are received directly from the radiator II with greaterintensity than the echoes thereof are received. Thus in the receiver the radiated pulses I5 and various echoes I6 thereof appear as indicated in Fig. 1. These pulses are, of course, amplified and rectified and supplied over a'con'ductor I! to one of the vertical deflection plates I8 of a cathode ray device I9.

This cathode ray device may have a viewing screen indicated by the circle 20 upon which the outgoing pulses l5 and the various echoes Ii; are caused to appear producing an indication such as that represented in Fig. 1 in the circle 20.

The cathode ray of the cathode ray device I9 deflected horizontally across the scale thereof by means of deflection voltage'applied between its horizontal deflection plates 2| from the output of an electron discharge device 8, the latter of- Which is controlled by a multivibrator compris- These discharge devices have their cathodes connected together and through a resistance 3'to ground. Their anodes are connected through individual resistors 22 and 23 to the positive side of the source of operating potential. This source of operating potential is indicated by plus and minus signs at the right hand side of the drawing, and is shunted by a potentiometer resistance 24. The discharge devices I and 2 are each provided with a control electrode, each of which is connected to ground through a, respective resistance 25 and 25. Condenser Zlis connected between the anode of the device I and the control electrode of the device '2 and cooperates'with resistances 22 and 28 to determine the duration of the successive periods in the cyclic operation of the generator comprising devices I and 2. This generator is synchronized with the radiated pulses by means of positive unidirectional pulses generated in the transmitter II) simultaneously with the radiated pulses which are su plied through sw tch 28, condenser 29 and resistance 30 to the oath.- odes of the two devices I and 2.

The operation of this generator comprising dischargedevices l and 2 and also the device .8 may best be explainedby referring to the curves of Fig. 2.

Let us consider this generator at a period in its operation when the discharge device I is conducting. This device passes current through rea sistance 22 and resistance 3, the bias on resistance 3 being sufficient to prevent the flow of anode current in the device 2. If now a positive pulse, such as those indicated at 18 in Fig. 2, be received from transmitter H) through elements 23, 29 and 3H upon the cathodes of the two devices, it tends to reduce the anode current in the device i. This reduction in anode current, of course, reduces the bias on device 2 and increases the anode potential on device I the latter of which is reflected in a more positive potential on the control electrode of device 2. Device 2' thus starts to pass current, producing increased bias on the resistance 3. This increased bias immediately interrupts the flow of anode current in the device I. The potential on the anode of device I does not immediately rise but is delayed in its rise by reason of the time required for condenser 21 to charge. The result is that the potential on the anode of device I rises in accordance with the rising portions 3| of the curve em of Fig. 2.

The charging current in condenser 21, however, rises immediately to its largest value, this current flowing through ressitance 26 and produc ng a positive bias on the grid of discharge device 2. This positive bias at its lar est value is indicated at 32 in the curve egz of Fig. 2. Of course, as the condenser charges its charging current'gradually diminishes in accordance with the slope 33 of the curve egz. The discharge device 2, however, is conducting during this period, its anode current gradually reducing. Its anode potential gradually rises from its lowered value in accordance with the portions 3 4 of the curve epz.

Condenser 21 finally becomes charged to such a point, and the anode current in device 2 is sufliciently reduced, to permit device I again to become conducting. When this occurs, th anode potential on device I drops to a low value thereby driving the grid of device 2 strongly negative as indicated by the portion 35 of the curve eg'z. Plate current in the device 2, of course,

then increases to the highest value indicated by the curve epz. Condenser 21 then discharges in accordance with the portions 36 of the curve egz through resistance 26, device! andresistance 3, this discharge continuing until finally a second synchronizing pulse arrives from the transmitter.

Resistance 3 is of low value relative to resistance 26 and the time of discharge of condenser 21 is determined practically entirely by resistance 25. This synchronizing pulse again causes the device 2 to become conducting, as previously described, and the cycle of operations is repeated.

The plate potential on the device 2 thus varies periodically in accordance with the curve cm of Fig. 2. This potential is supplied through the condenser 31 to the control electrode of electron discharge device 8 where it produces a variation in voltage indicated by the curve-eye of Fig. 2. This curve varies in shape somewhat from the curve em by reason of the differentiating action of the condenser 31, which is of large capacitance. However, when the voltage on the grid of discharge device -8 is driven negative, its anode current is interrupted, producing a rise in its anode voltage. The rate of rise of this anode voltage is determined .by 38, which is connected between the anode and cathode of this device through a selector switch 4|. This switch is arranged to be positioned in any of three positions to connect between the anode and cathode any of three condensers 38,

the capacity of a condenser iii) '4 V 39, or 48 having different capacities. Thus the voltage on the anode may be made to rise at any one of three rates as indicated by the slopes 42, 43 and 44 of the curve 629:; in Fig. 2. The voltage across this condenser is applied between the horizontal deflection plates 2| of the cathode ray tube and the rate of rise of this voltage thus determines the rate at which the beam in the cathode ray device is deflected horizontally across the screen. Thus, for example, if the condenser 38 be in circuit, the deflection across the viewing screen may be produced in the time that is required for a radiated pulse to travel to remote object 15 miles away and return. If condenser 39 be in circuit, the ray is deflected across the viewing screen in the time required for a pulse to travel to a remote object 75 miles away and return, and, similarly, if condensers 49 be included in the circuit, the ray is deflected across the screen more slowly and in a time required for the pulse to travel to a remote object 375 miles away and return. Thus the switch 40 determines the range of the equipment, and the slopes 42, 43 and 44 of the curve em in Fig. 2 bear the legends 15 miles, 75 miles and 375 miles, respectively, corresponding to the ranges of the equipment which may be determined by the switch 40.

It is desirable in the operation of equipment such as that described that means be provided to produce an indication upon the cathode ray screen to identify a particular echo, for example, which is indicated thereon. For this purpose the discharge device 45 is provided. The voltage on the anode of device 8 is supplied to the control electrode of this device and its cathode is connected through a resistance 46 to a variable contact 41 on the potentiometer resistance 24. When the anode potential ofdevice 8 is at its lowest value, device 45 is non-conducting by reason of the positive potential supplied to its cathode from resistance 24. However, as the voltage rises in accordance with the slopes 42, 43 and 44 of curve em, a point is reached Where device 45 becomes conducting and produces a voltage on resistance 46. This voltage is supplied to an amplifier and limiter '48 whereby it is limited to a fixed value and thenceito thelower anode 49 of the vertical deflection plates of the oathode ray tube. 'This potential produces 'thevertical deflection 49 shown in the circle 20 on the cathode ray oscillograph; that is, the cathode ray is deflected across the screen horizontally to a point where it is suddenly defiected'downwardly and then afterwards proceeds horizontally in its course across the screen. This deflection 49 may be caused to appear at any desiredpoint in the horizontal trace across the screen of the oscillograph by varying the contact 41, thus changing the point in the rise in anode voltage of device 8 where device 45becomes conducting. Thus the deflection 49 may be positioned to, coincide with the indication of any echo to be identified and particularly observed. a

' The equipment 53 comprises blanking equipment to interrupt the ray ofthecathode ray device at times other than during the forward trace across the fluorescent screen. It is supplied with theanode voltages of device .2 and responds to supply negative pulses to thecontrol electrode Eilof the cathode ray device, each pulse being suficiently long to interrupt the cathode ray during the entire time between completion of one forward trace and initiationo-E the next. .Switch 5i in this equipment is unicontrolled with. switch 4i and operates to effect suitable variation in the duration of these negative pulses to accommodate may be any suitable unilateral conducting device, but which preferably is a diode, to a load circuit comprising resistors 54, 55 and 56, The resistor 56 is shunted by the usual smoothing conmay be varied by varying the contact 59 on the resistance 56 thereby to vary the degree of focusing of the cathode ray upon the fluorescent screen.

The control electrode 60 of the cathode ray device is connected to a variable point on resistance 55 whereby the intensity of the cathode ray may be varied to control the brilliance of the indication produced upon the cathode ray screen.

It is frequently desirable in the operation of equipment such as that described to provide means for operation of the equipment when the transmitter I0 is not in operation and therefore when the synchronizing pulses from the transmitter ID are not available. To this end, means flows in the diode 53 at the peak of each alternate half cycle of the wave from the alternating source 52. Thus a brief pulse of current flows in the diode 53 and through resistors 54 and 55 at a frequency of 60 cycles per second, these being the brief pulses of current which restore the charge in the smoothing condenser 51, which leaks oJT through resistance 56 during the intermediate periods, this phenomena resulting in the familiar e ripple or hum voltage which occurs on such smoothing condensers. To derive corresponding pulses for the synchronizing of the generator I, 2, the resistance 6| and condenser 6| are connected across the output of the rectifier. These such as those indicated at iii in Fig. 2 and are of positive polarity, whereas those derived from resistance 6| are represented at H in Fig. 2 and are of negative polarity.

The circuit of the generator I, 2 is particularly advantageous for such synchronization because ts timing circuit, namely, the circuit 22, 21, 26, s isolated from these synchronizing circuits, in- :luding the switches 28 and 62, and thus the low impedance of these synchronizing circuits do not affect the time constants of the timing circuit 22, 21, 26. That is, as previously explained, the charging period of condenser 21 is determined by the resistances 22 and 26, this determining the duration of the negative pulses supplied to the grid of discharge device 8. The discharge period of the condenser 21 is controlled by resistance 26 since device i during this period is of very low impedance. This determines the duration of the positive pulse applied to the control electrode of device 8. This circuit 26, 21, 22, however, is isocircuits and thus the time constants thereof are totally unafiected by the impedance of the synchronizing circuits. This is important because the impedance of these synchronizing circuits resistance 72 of the order of 100 ohms, and the resistance 30 of the order of 1,000 ohms, these values being such that they would materially afiect the time constants of the timing circuit were it not for the fact that these circuits are isolated from the timing circuit by the space paths in the discharge devices I and 2.

While I have shown a particular embodiment will of course be understood that I do not wish to be limited thereto since various modifications both in the circuit arrangement and in the instrumentalities employed may be made without departing from the spirit and scope of my invention. I contemplate by the appended claims, however, to cover any such modifications as fall within the true spirit and. scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a cathode ray device, a source of alternating electromotive force, means to supply operating voltage to said cathode ray device, said means comprising means to produce peak rectification of said alternating electromotive force and to supply the resulting unidirectional voltage to said device, means to supply cyclically varying deflection voltage to said device to deflect the ray thereof, and means responsive to the residual pulsation in said uniditions with said pulses.

3. In combination; a cathode ray device, means to supply operating potential thereto, said means comprising a source of alternating voltage, a smoothing condenser, and a unilateral conduct- '7 synchronize, isai'd pulse'generator, and means to render said last'two means alternatively operative.

e. .In combination, a cathode ray device, means to supply operating potential thereto, said means comprising a source of alternating voltage, a smoothing condenser, and a unilateral conducting device connected between said source and condenser whereby periodic current pulses flow in said unilateral conducting device, a generator of periodic pulses for controlling said cathode ray device, said means comprising a cyclically operating multivibrator having means to con trol the duration of successive periods of its cyclical operation, said means comprising a circuit having predetermined time constants, means to apply synchronizing pulses derived either from an external source or from the current pulses in said unilateral conducting device to said multivibrator to synchronize its operation, and means to prevent said last means from afiecting the time constants of said timing circuit.

5. The combination, of a source of periodic pulses and pulses occurring between said periodic pulses, a cathode ray device, peak rectifying means to supply operating voltage to said cathode ray device, a deflection voltage generator, means to deflect the ray of said device in accordance with the voltage produced by said generator, and to control said ray during its deflection in accordance with said pulses occurring between said periodic pulses, and means to derive said periodic pulses from said source, or alternatively, from said peak rectifier, to synchronize said deflection voltage generator.

6. The combination, of a cathode ray device, a

' polarity from current periodic pulse source, a periodic deflection voltage generator, means to fdeflect the ray of said device in accordance with the voltage of-said generator during the period between th periodic pulses from said source, peak rectifier means to supply operating voltage to said device, means to produce periodic pulses of one polarity from current flowing in said rectifier, means to produce periodic pulses of opposite polaritysynchronous with the pulses of said periodic pulse source, and means to synchronizesaid deflection voltagegenerator with either of said periodic pulses.

7. The combination, of a cathode ray device, a source of periodic pulses, a generator producing cyclically varying deflection voltage, said generator comprising a pair of electron discharge devices and a timing circuit having time constants determining the duration of successive periods of its cyclical operation, means to deflect the ray of said device in accordance with said cyclically varying deflection voltage and to control saidray during said deflection, peak rectifying means to supply operating voltage to said device, means to produce periodic pulses of one flowing in said rectifier, means to produce periodic pulses of opposite .polarity synchronous with the periodic pulses of said source, means to supply pulses produced by either of said last two means to said generator to synchronize the operation thereof, and means utilizing the space paths in said discharge devices to isolate said last means from said timing circuit whereby the time constants of said timing circuit are not afiected by the impedance 35 of said synchronizing pulse supply means.

ROBERT E. MOE. 

